Which hair cells serve as the primary sensory receptors in the cochlea?

Which hair cells serve as the primary sensory receptors in the cochlea?

• A. Outer hair cells
• B. Supporting cells
• C. Vestibular hair cells
• D. Inner hair cells

Answer: (D)

Mechanotransduction of sound in the cochlea happens primarily at the inner hair cells. When the basilar membrane vibrates in response to a sound, the stereocilia of the inner hair cells bend. This deflection pulls on tip links that open mechanically gated ion channels, creating receptor potentials and triggering neurotransmitter release onto the auditory nerve fibers. Because inner hair cells provide the majority of afferent input to the spiral ganglion, they serve as the main sensory receptors converting mechanical energy into neural signals for hearing. Outer hair cells, in contrast, mainly act as amplifiers. Their electromotile motion, driven by prestin and regulated by efferent signals, enhances and sharpens basilar membrane motion to increase sensitivity and frequency selectivity, but they are not the primary transducers feeding the auditory nerve. Supporting cells mainly provide structural and ionic support for the organ of Corti, while vestibular hair cells are located in the balance organs and mediate head movement sensing, not hearing. So, the inner hair cells are the primary sensory receptors in the cochlea because they directly transduce mechanical sound energy into neural signals that reach the brain.

Mechanotransduction of sound in the cochlea happens primarily at the inner hair cells. When the basilar membrane vibrates in response to a sound, the stereocilia of the inner hair cells bend. This deflection pulls on tip links that open mechanically gated ion channels, creating receptor potentials and triggering neurotransmitter release onto the auditory nerve fibers. Because inner hair cells provide the majority of afferent input to the spiral ganglion, they serve as the main sensory receptors converting mechanical energy into neural signals for hearing.

Outer hair cells, in contrast, mainly act as amplifiers. Their electromotile motion, driven by prestin and regulated by efferent signals, enhances and sharpens basilar membrane motion to increase sensitivity and frequency selectivity, but they are not the primary transducers feeding the auditory nerve. Supporting cells mainly provide structural and ionic support for the organ of Corti, while vestibular hair cells are located in the balance organs and mediate head movement sensing, not hearing.

So, the inner hair cells are the primary sensory receptors in the cochlea because they directly transduce mechanical sound energy into neural signals that reach the brain.